uk.ac.starlink.table.formats

Class AsciiTableBuilder

java.lang.Object

uk.ac.starlink.table.formats.DocumentedTableBuilder

uk.ac.starlink.table.formats.AsciiTableBuilder

All Implemented Interfaces:

Documented, DocumentedIOHandler, TableBuilder

public class AsciiTableBuilder
extends DocumentedTableBuilder

A table builder which reads tables in simple ASCII format. The detailed format of input file which is understood is documented fully in the AsciiStarTable class.

Constructor Summary

Constructors

Constructor and Description
AsciiTableBuilder()

Method Summary

Modifier and Type	Method and Description
boolean	canImport(java.awt.datatransfer.DataFlavor flavor) Indicates whether this builder is able to turn a resource of media type indicated by flavor into a table.
boolean	canStream() Indicates whether this handler can read tables from a stream.
boolean	docIncludesExample() Indicates whether the serialization of some (short) example table should be added to the user documentation for this handler.
java.lang.String	getFormatName() Returns the name of the format which can be read by this handler.
java.lang.String	getXmlDescription() Returns user-directed documentation in XML format.
StarTable	makeStarTable(DataSource datsrc, boolean wantRandom, StoragePolicy policy) Constructs a StarTable based on a given DataSource.
void	setMaxSample(int maxSample) Sets the maximum number of rows that will be sampled to determine column data types.
void	streamStarTable(java.io.InputStream in, TableSink sink, java.lang.String pos) Reads a table from an input stream and writes it a row at a time to a sink.

Methods inherited from class uk.ac.starlink.table.formats.DocumentedTableBuilder

getExtensions, looksLikeFile

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface uk.ac.starlink.table.formats.DocumentedIOHandler

matchesExtension, readText, toLink

Constructor Detail

AsciiTableBuilder

public AsciiTableBuilder()

Method Detail

getFormatName

public java.lang.String getFormatName()

Description copied from interface: TableBuilder

Returns the name of the format which can be read by this handler. Matching against this string may be used by callers to identify or select this handler from a list.

Returns:

one-word description of this handler's format

canImport

public boolean canImport(java.awt.datatransfer.DataFlavor flavor)

Description copied from interface: TableBuilder

Indicates whether this builder is able to turn a resource of media type indicated by flavor into a table. It should return true if it thinks that its TableBuilder.streamStarTable(java.io.InputStream, uk.ac.starlink.table.TableSink, java.lang.String) method stands a reasonable chance of successfully constructing a StarTable from a DataSource whose input stream is described by the DataFlavor flavor. It will typically make this determination based on the flavor's MIME type.

This method should only return true if the flavor looks like it is targeted at this builder; for instance a builder which uses a text-based format should return false for a flavor which indicates a MIME type of text/plain.

This method is used in supporting drag and drop functionality (see StarTableFactory.canImport(java.awt.datatransfer.DataFlavor[])).

Parameters:

flavor - the DataFlavor whose suitability as stream input is to be assessed

Returns:

true iff this builder reckons it stands a good chance of turning a stream of type flavor into a StarTable

makeStarTable

public StarTable makeStarTable(DataSource datsrc,
                               boolean wantRandom,
                               StoragePolicy policy)
                        throws TableFormatException,
                               java.io.IOException

Description copied from interface: TableBuilder

Constructs a StarTable based on a given DataSource. If the source is not recognised or this builder does not know how to construct a table from it, then a TableFormatException should be thrown. If this builder thinks it should be able to handle the source but an error occurs during processing, an IOException can be thrown.

The wantRandom parameter is used to indicate whether, ideally, a random-access table should be returned. There is no requirement for the builder to honour this request, but if it knows how to make both random and non-random tables, it can use this flag to decide which to return.

Note: the presence of the wantRandom parameter is somewhat misleading. TableBuilder implementations usually should, and do, ignore it (it would be removed from the interface if it were not for backward compatibility issues). Regardless of the value of this parameter, implementations should return a random-access table only if it is easy for them to do so; in particular they should not use the supplied storagePolicy, or any other resource-expensive measure, to randomise a sequential table just because the wantRandom parameter is true.

Parameters:

datsrc - the DataSource containing the table resource

wantRandom - whether, preferentially, a random access table should be returned

policy - a StoragePolicy object which may be used to supply scratch storage if the builder needs it

Returns:

a StarTable made out of datsrc

Throws:

TableFormatException - if the table is not of a kind that can be handled by this handler

java.io.IOException - if an unexpected I/O error occurs during processing

streamStarTable

public void streamStarTable(java.io.InputStream in,
                            TableSink sink,
                            java.lang.String pos)
                     throws TableFormatException

Description copied from interface: TableBuilder

Reads a table from an input stream and writes it a row at a time to a sink. Not all implementations will be able to do this; for instance, extracting the table from the data may be a two-pass process. Implementations which are unable to perform this function should throw a TableFormatException.

The input stream should be prepared for use prior to calling this method, so implementations should not in general attempt to decompress or buffer istrm.

Parameters:

in - input stream containing table data

sink - destination of the table

pos - position identifier describing the location of the table within the stream; see DataSource.getPosition() (may be null)

Throws:

TableFormatException - if the table can't be streamed or the data is malformed

canStream

public boolean canStream()

Description copied from class: DocumentedTableBuilder

Indicates whether this handler can read tables from a stream.

Specified by:

canStream in class DocumentedTableBuilder

Returns:

true iff this handler can read from streams

docIncludesExample

public boolean docIncludesExample()

Description copied from interface: DocumentedIOHandler

Indicates whether the serialization of some (short) example table should be added to the user documentation for this handler. Binary formats, or instances for which the Documented.getXmlDescription() method already includes some example output, should return false.

Returns:

true if the user documentation would benefit from the addition of an example serialization

getXmlDescription

public java.lang.String getXmlDescription()

Description copied from interface: Documented

Returns user-directed documentation in XML format.

The output should be a sequence of one or more <P> elements, using XHTML-like XML. Since rendering may be done in a number of contexts however, use of the full range of XHTML elements is discouraged. Where possible, the content should stick to simple markup such as the elements P, A, UL, OL, LI, DL, DT, DD EM, STRONG, I, B, CODE, TT, PRE.

Returns:

XML description of this object

setMaxSample

@ConfigMethod(property="maxSample",
              doc="<p>Controls how many rows of the input file are sampled\nto determine column datatypes.\nWhen reading ASCII files, since no type information is present\nin the input file, the handler has to look at the column data\nto see what type of value appears to be present\nin each column, before even starting to read the data in.\nBy default it goes through the whole table when doing this,\nwhich can be time-consuming for large tables.\nIf this value is set, it limits the number of rows\nthat are sampled in this data characterisation pass,\nwhich can reduce read time substantially.\nHowever, if values near the end of the table differ\nin apparent type from those near the start,\nit can also result in getting the datatypes wrong.\n</p>",
              usage="<int>",
              example="5000")
public void setMaxSample(int maxSample)

Sets the maximum number of rows that will be sampled to determine column data types.

Parameters:

maxSample - maximum number of rows sampled; if <=0, all rows are sampled